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Xenix is a discontinued version of the Unix operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s. The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and eventually replaced it by SCO UNIX (now known as SCO OpenServer). In the mid-to-late 1980s, Xenix was the most common Unix variant, measured according to the number of machines on which it was installed. Microsoft chairman Bill Gates said in 1996 that for a long time his firm had the highest-volume AT&T Unix license. ==History== Bell Labs, Unix's developer, was part of the regulated Bell System and could not sell Unix. It instead licensed the software to others. Microsoft, which expected that Unix would be its operating system of the future when personal computers became powerful enough, purchased a license for Version 7 Unix from AT&T in 1978, and announced on August 25, 1980 that it would make it available for the 16-bit microcomputer market.〔http://channel9.msdn.com/Series/History/The-History-of-Microsoft-1980〕 Because Microsoft was not able to license the "UNIX" name itself, the company gave it an original name. Microsoft, in turn, did not sell Xenix directly to end users; instead, they licensed it to OEMs such as IBM, Intel, Tandy, Altos, SCO, and Siemens (SINIX) who then ported it to their own proprietary computer architectures. Microsoft Xenix originally ran on the PDP-11. The first port was for the Zilog Z8001 16-bit processor: the first customer ship was January 1981 for Central Data Corporation of Illinois,〔 followed in March 1981 by Paradyne Corporation's Z8001 product.〔 The first 8086 port was for the Altos Computer Systems' non-PC-compatible 8600-series computers (first customer ship date Q1 1982).〔The Altos 8086 machines had a custom MMU, which used 4K pages.〕〔 Intel sold complete computers with Xenix under their Intel System 86 brand (with specific models such as 86/330 or 86/380X); they also offered the individual boards that made these computers under their iSBC brand. This included processor boards like iSBC 86/12 and also MMU boards such as the iSBC 309. The first Intel Xenix systems shipped in July 1982.〔〔Intel also offered their own iRMX operating system as an alternative for these.〕 Tandy more than doubled the Xenix installed base when it made TRS-XENIX the default operating system for its TRS-80 Model 16 68000-based computer in early 1983, and was the largest Unix vendor in 1984. Seattle Computer Products also made (PC-incompatible) 8086 computers bundled with Xenix, like their Gazelle II, which used the S-100 bus and was available in late 1983 or early 1984.〔〔http://bitsavers.trailing-edge.com/pdf/seattleComputer/brochures/Gazelle_II.pdf〕 There was also a port for IBM System 9000.〔BYTE Guide to the IBM PC, fall 1984, p.61〕 SCO had initially worked on their own PDP-11 port of V7, called Dynix,〔Unrelated to the later Dynix from Sequent Computer Systems〕 but then struck an agreement with Microsoft for joint development and technology exchange on Xenix in 1982. In 1984, a port to the 68000-based Apple Lisa was jointly developed by SCO and Microsoft and it was the first shrink-wrapped binary product sold by SCO. The difficulty in porting to the various 8086 and Z8000-based machines, said Microsoft in its 1983 OEM directory, had been the lack of a standardized memory management unit and protection facilities. Hardware manufacturers compensated by designing their own hardware, but the ensuing complexity made it "extremely difficult if not impossible for the very small manufacturer to develop a computer capable of supporting a system such as XENIX from scratch," and "the XENIX kernel must be custom-tailored to each new hardware environment."〔(Microsoft Xenix Operating System OEM Directory, May 1, 1983, Part No. OEM0091B )〕 A generally available port to the ''unmapped'' Intel 8086/8088 architecture was done by The Santa Cruz Operation around 1983.〔(【引用サイトリンク】 publisher = Operating System Documentation Project )〕 SCO Xenix for the PC XT shipped sometime in 1984 and contained some enhancement from 4.2BSD; it also supported the Micnet local area networking. The later 286 version of Xenix leveraged the integrated MMU present on this chip, by running in 286 protected mode.〔(Microsoft Xenix 3.0 ready for 286 )〕 The 286 Xenix was accompanied by new hardware from Xenix OEMs. For example, the Sperry PC/IT, an IBM PC AT clone, was advertised as capable of supporting eight simultaneous dumb terminal users under this version. While Xenix 2.0 was still based on Version 7 Unix, version 3.0 was upgraded to a Unix System III code base,〔 A 1984 Intel manual for Xenix 286 noted that the Xenix kernel had about 10,000 lines at this time.〔 It was followed by a System V.2 codebase in Xenix 5.0 (aka Xenix System V). Microsoft omitted multiuser support from its own MS-DOS operating system because Xenix had it. The company planned to over time improve MS-DOS so it would be almost indistinguishable from single-user Xenix, or XEDOS, which would also run on the 68000, Z8000, and LSI-11; they would be upwardly compatible with Xenix, which ''Byte'' in 1983 described as "the multi-user MS-DOS of the future". Microsoft advertised DOS and Xenix together, listing the shared features of its "single-user OS" and "the multi-user, multi-tasking, UNIX-derived operating system", and promising easy porting between them. After the breakup of the Bell System, however, AT&T started selling Unix. Microsoft, believing that it could not compete with Unix's developer, decided to abandon Xenix. The decision was not immediately transparent, and so Xenix gave birth to the term vaporware. An agreement was signed with IBM to develop OS/2, and the Xenix team (together with the best MS-DOS developers) was assigned to that project. In 1987 Microsoft transferred ownership of Xenix to SCO in an agreement that left Microsoft owning 25% of SCO. When Microsoft eventually lost interest in OS/2 as well, it based its further high-end strategy on Windows NT. In 1987, SCO ported Xenix to the 386 processor, a 32-bit chip, this after securing knowledge from Microsoft insiders that Microsoft was no longer developing Xenix.〔 Xenix System V release 2.3.1 introduced support for i386, SCSI and TCP/IP. SCO's Xenix System V/386 was the first 32-bit operating system available on the market for the x86 CPU Architecture. Microsoft continued to use Xenix internally, submitting a patch to support functionality in UNIX to AT&T in 1987, which trickled down to the code base of both Xenix and SCO UNIX. Microsoft is said to have used Xenix on Sun workstations and VAX minicomputers extensively within their company as late as 1992. All internal Microsoft email transport was done on Xenix-based 68000 systems until 1995-96, when the company moved to its own Exchange Server product.〔(【引用サイトリンク】 url = http://www.microsoft.com/technet/archive/itsolutions/intranet/build/exchgdep.mspx#EGAA )〕 SCO released its SCO UNIX as a higher-end product, based on System V.3 and offering a number of technical advances over Xenix; Xenix remained in the product line. In the meantime, AT&T and Sun Microsystems completed the merge of Xenix, BSD, SunOS and System V.3 into System V Release 4. The last version of SCO Xenix/386 itself was System V.2.3.4, released in 1991. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Xenix」の詳細全文を読む スポンサード リンク
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